Rockets, particularly model rockets, have been recovered from flight using a variety of methods. Examples include crash recovery, nose blow recovery, parachute recovery, streamer recovery, retrorocket recovery, tumble recovery, and glide recovery. Virtually all previous modes of recovery, except crash recovery, require moving parts. Crash recovery, while having been used in practice, is obviously the least satisfactory method because of damage to the rocket and hazard to persons and objects on the ground. Nose blow recovery, when used in full sized rockets, offers substantial improvement in the salvageability of rocket and payload components. Used in model rocketry, nose blow recovery has been called float recovery. In nose blow recovery the ejection of the nose cone destabilizes the rocket such that the main section of the rocket floats or glides. Parachute recovery is a notorious method used routinely to recover rockets safely. Streamer recovery is based on the aerodynamic drag created by a long narrow sheet attached to the rocket with an appropriate line. Retrorocket recovery is based upon the firing of rockets to slow descent of the rocket before impact. Tumble recovery relies on shifting the center of gravity of a rocket causing the rocket to be unstable. The unstable rocket tumbles, creating substantial drag, which slows the descent of the rocket.
Glide recovery may be used to recover part or all of a rocket. When part of the rocket is recovered as a glider, it is termed a boost glider. When the entire rocket, including the engine, is recovered as a glider, it is termed a rocket glider. Previous means of glide recovery have used separation of parts, movement of aerodynamic surfaces, or a shift in center of gravity to transition from a near vertical rocket launch to glide recovery. The instant invention is primarily, but not exclusively, useful as a rocket glider. This invention uses a side thrust port or sideways thrusting means, on a rocket with fixed aerodynamic geometry and fixed center of gravity, to change the stability from narrow angle forward stability to a gliding rearward stability. The center of gravity may incidentally move forward during flight due to the consumption of fuel in a rearward mounted engine.
U.S. Pat. No. 3,114,317, Estes, when reduced to practice, uses a side thrust port but not a fixed center of gravity or glide recovery as in the current invention. Estes teaches a rearward shift in center of gravity for tumble recovery. U.S. Pat. No. 3,157,960, Schutz et al uses glide recovery but lacks the fixed aerodynamic geometry and the fixed engine of the current invention. Goddard, Goddard and Pendray, ROCKET DEVELOPMENT LIQUID-FUEL ROCKET RESEARCH 1929-1941 discloses sideways recovery of a rocket with a gyroscopically controlled moveable tail casing. Schutz et al, along with Goddard, Goddard and Pendray, teach a shift in aerodynamic surfaces including fin flaps and moveable fins, for rocket glide recovery. U.S. Pat. No. 3,452,471, Street, pop pod glider uses glide recovery but lacks the fixed center of gravity of the current invention. Street teaches a rearward shift in the center of gravity due to the loss of the engine assembly for glide recovery. Certain similar designs rely only on the loss of engine propellant in a forward mounted engine to shift the center of gravity rearward. The AVI ASTROPORT advertising flyer LINAEUS GIGANTUS uses a tall rocket with a large length to diameter ratio and ejectable nose cone for a rearward gliding recovery but lacks the side thrust port of the current invention AVI ASTROPORT teaches a shift in a shift in aerodynamic surfaces or nose ejection and an effective rearward shift in center of gravity for glide or float recovery. Taken individually or in combination, these examples of prior art teach that the center of gravity or center of pressure of a rocket must be changed by physical means to allow for glide recovery of a rocket. In particular the center of gravity must be moved rearward, often using moving parts, or the center of pressure forward by the use of moving parts for a successful transition from rocket to glider.
U.S. Pat. No. 2,841,084, Carlisle, is the basic patent for model rockets specifying a model rocket engine. Specifically a model rocket engine contains a propellant train, a delay train and an ejection charge. The delay train allows the rocket to coast to an appropriate altitude after being boosted by the propellant. The ejection charge is used for deploying the recovery device. It is the ejection charge that provides the sideways thrusting means when directed through the side thrust port of the current invention. Engine ejection is when the ejection charge of the rocket engine explodes. Model rockets are defined as weighing less than 1 pound (454 grams) and having less than 4 ounces (113 grams) of propellant. Large model rockets are defined as exceeding either of those limits yet weighing less than 1500 grams and having less than 125 grams of propellant.
Barrowman, Technical Information Report 33 CALCULATING THE CENTER OF PRESSURE OF A MODEL ROCKET, discloses the detailed method of determining the Barrowman Center of Pressure. Estes, Technical Report TR-1 Rocket Stability, discloses a method of Lateral Area Calculations for determining center of pressure. Taylor, Technical Report TR-9 Designing Stable Rockets, discloses the detailed method of Center Lateral Area calculations for determining center of pressure. These publications were produced by Centuri Engineering and Estes Industries, respectively. These companies have merged since publication.